Breast carcinoma is a leading cause of death among women in this country. Clinical trials have shown that early treatment in an adjuvant setting permits the saving of many lives by preventing disease recurrence, presumably by treating subclinical micrometastases. Adjuvant treatment is based on the clinical evaluation of patients. Based on these evaluations, it is not administered to a significant number of patients who may have clinical undetectable disease. Some of these women eventually relapse and die of breast carcinoma. A system that would predict the presence or absence of metastases could lead to the identification of those patients who would benefit from adjuvant therapy in the absence of clinical detectable disease. Preliminary studies utilizing biomatrix, an extracellular matrix extracted from different tissues, have indicated that it is tissue specific as a cell culture substrate for long-term survival and growth of normal cells. Neoplastic cells have a less strict specificity for types of biomatrix substrates. In a few tumors studied (colon and prostate), there was a correlation between growth on specific types of biomatrix and the site specificity for metastases in the patient. Based on these studies, we want to test whether the growth of malignant tissue on particular types of extracellular matrix can prove predictive of in vivo metastatic potential. The hypothesis will be tested using normal mammary epithelial cells with two different human breast carcinoma cell lines. We will compare the patterns of growth of these cell populations on various types of biomatrix. The metastatic potential of the cell lines in vivo will be assessed by injecting the cells into athymic nude mice treated with antibodies to mouse interferon. Should the basic research provide evidence for the hypothesis, a clinical screen of patients with breast tumors would be made. Breast tumors from patients with variable extent of metastatic disease would be assessed for their ability to grow on various types of biomatrix. The tumors would be assessed for their metastatic potential in athymic nude mice immunosuppressed with anti-interferon.